Ground Sphere Initial Questions v0.2

Project Background Questions

BQ1. Why are we making this?

BA1. The Ground Sphere CubeSat Ground Station is being built specifically to receive ""tweets from space" which will be broadcast by the SkyCube CubeSat. A side effect of having such a low cost and easy to use ground station is the educational opportunities in areas including satellite orbits, radio technology, telecommunications, and programming.

BQ2. Who is this for?

BA2. The Ground Sphere CubeSat Ground Station is for SkyCube backers, students, teachers, scouting troupes, space enthusiasts, and anyone who wants to directly experience satellite communications and participate in the SkyCube mission.

BQ3. How will this be used?

BA3. Ground station operators will use the ground station and its accompanying software to:

  1. Predict when the SkyCube (and other satellites) will be flyover the ground station site
  2. Use the Software Defined Radio (SDR) to receive the radio transmissions from SkyCube (and other satellites operating on the nearby frequencies)
  3. Decode the data packets from the SkyCube to read the "tweets" from space

BQ4. Who's going to build this?

BA4. The designs will be open so that anyone, without necessarily a technical education in amateur radio or satellite operations, would be able to build and operate a Ground Sphere CubeSate Ground Station. Note, the first kits will be built by SkyCube KickStarter backers.

Technical Requirement Questions

TQ1a. What features does it need to have (now)?

TA1a. The project needs to:

  • Predict when the SkyCube satellite will flyover the ground station and be within signal reception range
  • Receive radio signals on 915 MHz
  • Decode BPSK-modulated, unencrypted AX.25 data packets sent at 9600 baud
  • Be easy to assemble from kit components and only require simple tools (screw drivers, pliers, wrenches, etc) for assembly
  • Have low shipping costs for the packaged kit
  • All software required to operate the ground station must run on a Windows PC
  • The ground station radio must connect to the ground station computer through a commonly available port (for example: USB)
  • The ground station hardware should minimize the opportunity for mechanical failures (from things such as broken connectors or a lack of strain relief)
  • The ground station needs to account for Doppler shift during satellite flyovers

TQ1b. What features does it need to have (later)?

TA1b. In the future, the project (or related projects) may need to:

  • Predict when other satellites will fly over the ground station and be within signal reception range
  • Decode other data formats commonly used by CubeSats
  • Share radio signal with other users over Internet connections, so users can listen to satellite signals remotely
  • All software required to operate the ground station must run on Windows, OS X, and Linux

TQ2. What are the legacy requirements?

TA2. To maintain compatibility with other projects, the system should:

  • N/A

Project Requirement Questions

PQ1. How many do we want to make?

PA1. As an open source hardware kit, the long term objective is to promote and sell as many ground station kits to as large of an audience (schools, scouting troupes, makerspaces, space enthusiasts, etc) as possible. However, the narrow focus on supporting SkyCube operations with the Ground Sphere may limit the number of kits which will be sold for this specific ground station, especially since the SkyCube is going to be on orbit for a very limited period of time. The sales lifetime of this specific kit (and in turn the number of kits we will want to sell) will depend on how many other satellites there are to observe in the same frequency range as the SkyCube. Note, there are approximately 2700 backers of the SkyCube KickStarter, of which Southern Stars is committed to delivering ground stations to between 20 and 30 backers. This gives a minimum number of ground stations to be built of 30 +/- 5, which would cover the minimum backers and a handful for Mach 30's use.

The timing of the project may also limit the scale of the initial run Mach 30 can produce. This decision will be revisited later in the development process (after the second prototype) to allow the development team to address the manufacturing logistics.

PQ2. What is the budget?

PA2. The materials cost should be kept under $100 to limit the retail cost of the kit. There are currently three prototypes planned. The project budget should cover all three prototypes plus overage. To that end, the threshold project budget (max) is $500 and the objective is $400.

PQ3. What is the timeline?

PA3. The timeline for this project is dictated by the SkyCube launch and deployment timeline. SkyCube is currently scheduled to be launched in December 2013, with deployment from the ISS in Q1 or Q2 of 2014. Southern Stars has stated they would be comfortable with a February 2014 delivery date for the kits. This gives a kit completion date of early January 2014 to give enough time to spool up manufacturing and shipping for the February due date.

PQ4. What waste products will be produced by the manufacture and/or operation of this?


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